(Objective-C) Sign MIME using RSASSA-PSS with SHA256

Demonstrates how to sign an MIME using the RSASSA-PSS signing algorithm with the SHA256 hash algorithm.

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

#import <CkoMime.h>
#import <CkoStringBuilder.h>
#import <CkoPfx.h>
#import <CkoCert.h>

// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

BOOL success;
CkoMime *mime = [[CkoMime alloc] init];

// Create a MIME message to sign.
[mime NewMultipartMixed];
[mime AddHeaderField: @"someHeader1" value: @"Some value 1"];
[mime AddHeaderField: @"someHeader2" value: @"Some value 2"];

CkoMime *part0 = [[CkoMime alloc] init];
[part0 AddHeaderField: @"hdrA" value: @"Some value A"];
[part0 AddHeaderField: @"hdrB" value: @"Some value B"];
part0.ContentType = @"text/plain";
[part0 SetBody: @"This is the plain-text body."];

CkoMime *part1 = [[CkoMime alloc] init];
[part1 AddHeaderField: @"hdrX" value: @"Some value X"];
[part1 AddHeaderField: @"hdrY" value: @"Some value Y"];
part1.ContentType = @"text/xml";
[part1 SetBody: @"<a>This is the XML body</a>"];

[mime AppendPart: part0];
[mime AppendPart: part1];

// The MIME to be signed:
CkoStringBuilder *sbUnsignedMime = [[CkoStringBuilder alloc] init];
[mime GetMimeSb: sbUnsignedMime];
NSLog(@"%@",[sbUnsignedMime GetAsString]);

// 	Content-Type: multipart/mixed; boundary="------------080303020600020604010008"
// 	someHeader1: Some value 1
// 	someHeader2: Some value 2
// 
// 	--------------080303020600020604010008
// 	hdrA: Some value A
// 	hdrB: Some value B
// 	Content-Type: text/plain
// 
// 	This is the plain-text body.
// 	--------------080303020600020604010008
// 	hdrX: Some value X
// 	hdrY: Some value Y
// 	Content-Type: text/xml
// 
// 	<a>This is the XML body</a>
// 	--------------080303020600020604010008--
// 

// Get a digital certificate with private key from a .pfx
// (Chilkat has many different ways to provide a cert + private key for siging.
// Using a PFX is just one possible option.)
CkoPfx *pfx = [[CkoPfx alloc] init];
success = [pfx LoadPfxFile: @"qa_data/rsassa-pss/privatekey.pfx" password: @"PFX_PASSWORD"];
if (success != YES) {
    NSLog(@"%@",pfx.LastErrorText);
    return;
}

// Get the certificate to be used for signing.
// (The typical case for a PFX is that it contains a cert with an associated private key,
// as well as other certificates in the chain of authentication.  The cert with the private
// key should be in the first position at index 0.)
CkoCert *cert = [pfx GetCert: [NSNumber numberWithInt: 0]];
if (pfx.LastMethodSuccess != YES) {
    NSLog(@"%@",pfx.LastErrorText);
    return;
}

// Indicate that RSASSA-PSS with SHA256 should be used.
mime.SigningAlg = @"pss";
mime.SigningHashAlg = @"sha256";

// Add a detached signature.
success = [mime AddDetachedSignature: cert];
if (success != YES) {
    NSLog(@"%@",mime.LastErrorText);

    return;
}

// Show the clear-signed MIME. (see the sample output below)
NSLog(@"%@",@"-------------------------------------------------------------");
NSLog(@"%@",@"Clear-signed MIME using detached signature:");
NSLog(@"%@",@"-------------------------------------------------------------");
NSLog(@"%@",[mime GetMime]);

// Restore the original unsigned MIME, and this time create an opaque signature.
[mime LoadMime: [sbUnsignedMime GetAsString]];

// Sign using an opaque signature
success = [mime ConvertToSigned: cert];
if (success != YES) {
    NSLog(@"%@",mime.LastErrorText);

    return;
}

// Show the opaque-signed MIME. (see the sample output below)
NSLog(@"%@",@"-------------------------------------------------------------");
NSLog(@"%@",@"Opaque-signed MIME :");
NSLog(@"%@",@"-------------------------------------------------------------");
NSLog(@"%@",[mime GetMime]);

NSLog(@"%@",@"Success.");

// -----------------------------------------------
// This is sample output for the clear-signed MIME:
// -----------------------------------------------
// 
// 	Content-Type: multipart/signed; boundary="----=_NextPart_672_c95a_97b64c9a.90b5204d";
// 	 protocol="application/x-pkcs7-signature";
// 	 micalg=sha256
// 
// 	------=_NextPart_672_c95a_97b64c9a.90b5204d
// 	Content-Type: multipart/mixed; boundary="------------030207090102000301050504"
// 	someHeader1: Some value 1
// 	someHeader2: Some value 2
// 
// 	--------------030207090102000301050504
// 	hdrA: Some value A
// 	hdrB: Some value B
// 	Content-Type: text/plain
// 
// 	This is the plain-text body.
// 	--------------030207090102000301050504
// 	hdrX: Some value X
// 	hdrY: Some value Y
// 	Content-Type: text/xml
// 
// 	<a>This is the XML body</a>
// 	--------------030207090102000301050504--
// 
// 	------=_NextPart_672_c95a_97b64c9a.90b5204d
// 	Content-Transfer-Encoding: base64
// 	Content-Type: application/x-pkcs7-signature; name="smime.p7s"
// 	Content-Disposition: attachment; filename="smime.p7s"
// 
// 	MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg
// 	ggL4MIIC9DCCAl2gAwIBAgIJAMPsJCT11cniMA0GCSqGSIb3DQEBCwUAMIGSMQswCQYDVQQGEwJB
// 	VTERMA8GA1UECAwIVmljdG9yaWExEjAQBgNVBAcMCU1lbGJvdXJuZTEhMB8GA1UECgwYSW50ZXJu
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// 	neC8qw==
// 
// 	------=_NextPart_672_c95a_97b64c9a.90b5204d--
// 

// -----------------------------------------------
// This is sample output for the opaque-signed MIME:
// -----------------------------------------------
// 	Content-Type: application/x-pkcs7-mime; name="smime.p7m"; smime-type="signed-data"
// 	someHeader1: Some value 1
// 	someHeader2: Some value 2
// 	Content-Disposition: attachment; filename="smime.p7m"
// 	Content-Transfer-Encoding: base64
// 
// 	MIIItAYJKoZIhvcNAQcCoIIIpTCCCKECAQExDzANBglghkgBZQMEAgEFADCCAdYGCSqGSIb3DQEH
// 	AaCCAccEggHDQ29udGVudC1UeXBlOiBtdWx0aXBhcnQvbWl4ZWQ7IGJvdW5kYXJ5PSItLS0tLS0t
// 	LS0tLS0wMDA2MDcwNzA3MDcwMTA1MDAwMTA5MDciDQpzb21lSGVhZGVyMTogU29tZSB2YWx1ZSAx
// 	DQpzb21lSGVhZGVyMjogU29tZSB2YWx1ZSAyDQoNCi0tLS0tLS0tLS0tLS0tMDAwNjA3MDcwNzA3
// 	MDEwNTAwMDEwOTA3DQpoZHJBOiBTb21lIHZhbHVlIEENCmhkckI6IFNvbWUgdmFsdWUgQg0KQ29u
// 	dGVudC1UeXBlOiB0ZXh0L3BsYWluDQoNClRoaXMgaXMgdGhlIHBsYWluLXRleHQgYm9keS4NCi0t
// 	LS0tLS0tLS0tLS0tMDAwNjA3MDcwNzA3MDEwNTAwMDEwOTA3DQpoZHJYOiBTb21lIHZhbHVlIFgN
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// 	IHRoZSBYTUwgYm9keTwvYT4NCi0tLS0tLS0tLS0tLS0tMDAwNjA3MDcwNzA3MDEwNTAwMDEwOTA3
// 	LS0NCqCCAvgwggL0MIICXaADAgECAgkAw+wkJPXVyeIwDQYJKoZIhvcNAQELBQAwgZIxCzAJBgNV
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// 	MIGSMQswCQYDVQQGEwJBVTERMA8GA1UECAwIVmljdG9yaWExEjAQBgNVBAcMCU1lbGJvdXJuZTEh
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// 	/QTfrLOuzXKy
//